Do You Calculate Your Own Personal EI

Ian-Barber

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Ok so I hold my hand up, I don't calculate my own personal EI for film although I would if I was fully confident in doing the test. I probably like many just err on the side of caution and over expose the film by 1 stop by setting the light meter to 1/2 box speed.

Do you actually do the EI test and have you seen much deviation from the manufactures recommended ISO.?
 

alexmuir

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I’ve done tests over the years, but not recently. I started using a method whereby you make visual comparisons of negative density against a thing called a Kodak Projection Print Scale. I wasn’t very good at that, although it is a workable method. I then spotted a transmission densitometer at a good price, and bought that. It’s much easier to use.
I have found some deviation from published figures, always downward. Halving the quoted speed is a fairly good starting point, although some films perform nearer their nominal rating. I found Delta 400 in Ilfosol 3 worked at 320, TMax100 at 64 in the same developer and TriX at 200, again in Ilfosol3.
The only time a higher speed was suggested, the camera required a service. It was a Nikon F3, of which I have two, and they now agree with each other.
I don’t think you would necessarily gain much by altering your current practice. If I use a film I haven’t tested, I do what you do, and downrate by one stop.
Alex


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David M

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Although it's usually described as testing the film, it's really resting the whole process.
Everybody's methods differ slightly, and differ in multiple details – choice of developer and dilution, agitation pattern, accuracy of thermometer, the point at which we start the timer, speed of emptying and filling the tank, temperature of the room or our hands, and the cheerfulness of the goldfish, for all I know.
Our shutter, our method of metering and the accuracy of our meter are obvious factors, as is our perception of what constitutes each Zone. (We commonly visualise the Zones as a staircase, but in the real world, they are a slippery slope.) It's easy to add a few more, if we are bored during a long exposure.
If these factors vary randomly, they may well cancel each other out, but it's quite possible that they all tend in the same direction (and our neighbour's details may tend in the other.) Altering the setting on our meter is an easy way to summarise everything, without carrying tables of correction factors around.
All this is mechanical, but we add aesthetic choices to the cauldron. What sort of scene makes us spread the tripod legs? Just how much shadow detail will satisfy us? What do we consider to be a good print anyway? (What does our mentor think of the prints we make now?)
How much do we value ease of printing over other qualities? Do we look forward the adventure of multiple timer re-setting and multiple filtration? Do we value a really good black over other qualities?
Are we printing in the darkroom at all, or are we scanning?
Is the siren call of recreational densitometry tempting us toward the rocks of absolute precision? How much do we enjoy constructing graphs?
All these factors, physical and personal, are summed up in the simple action of turning the speed dial on our meter. A few (more) simple tests to establish our N-0 developing time (and for the really picky, a few more for plus and minus) and off we go.
In practice, until we have made enough mistakes, we don't have a useful amount of data on the problems we wish to solve, and halving the box speed and reducing development by about 20% seem to suffice for almost everybody, so there's no rush.
But sooner or later, it will seem worthwhile to do the tests. Until we've done it, we will have little niggly doubts. "Could things be better?" will sit at the back of the mind until we've wasted those few sheets of film. A well-developed curiosity should be part of every photographer's mental baggage.
 

Ian Grant

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I did a lot of testing about 30 years ago to find the best film/developer combinations that suited me and my ways of working. Having concluded that I would use Agfa AP100 in Rodinal I then used Zone System testing to determine the effective EI and development time, surprisingly my EI was box speed and time matched Agfa's own recommendation. Testing was a two step process, first to determine the probable. effective EI, second to determine the ideal dev time to print on a chosen paper and grade. If the ideal dev time was significantly different to the one used in the first test that could affect the effective EI, however in practice they were close enough to make mo difference.

My back up film was Tmax100, and Tmax400 for some hand held work (MF) again in Rodinal but both at half box speed same development time as the AP100. I also used EFKE PL25 now the box speed as indicates by the name is actually its Tungsten light speed, its listed daylight speed was 40 ISO, testing gave me an effective EI of 50.

AP100 was replaced by APX100 which behaved the same anyway, but I'd often be processing sheets of APX100, Tmax100 or EFKE25 together in the same tank:

Agfa APX100 @ 100 EI
Tmax 100 @ 50 EI
EFKE 25 @ 50 EI

In more recent years I switched to Ilford Delta 100 & 400 plus HP5 for hand-held LF work and Fomapan 100/200 as my back up films both at half their box speeds and with reduces development to control the contrast.

It's important to remember that films have a different speed in Tungsten light compared to daylight, how much depends on the spectral sensitivity of the emulsion. With FP4 Ilford gave an ISO speed of 80 in Tungsten light on older data sheets, Ortho Plus is slower 40 ISO in Tungsten light compared to 80 ISO in daylight. Tungsten studio lighting was once quite common but is rarely used these days so manufacturers stopped listing the Tungsten speed but it's still an issue with some room lighting etc.

Ian
 

David M

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A very interesting post. Thank you.
It might be a trivial detail, but would photographing near to sunset, when the light is also redder, affect film speed? A reduction in sensitivity might look like reciprocity.
 

Ian Grant

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Yes, the shift in colour temperature will have an effect, that's why reciprocity failure isn't as simple in all situations as charts or Ilford's equation would indicate.

Should add that the tungsten light ISO speeds were for Photofloods which run hotter than the domestic tungsten bulbs we used for household lighting and had a higher colour temperature 3200k, daylight is typically 5500-6000k, standard incandescent (tungsten) lamps were 2400k.

Actually light at sunset/sunrise is typically 3200k similar to a tungsten bulb.

Ian
 
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David M

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So, a colour temperature meter to add to the mule's panniers. The LF life is cruel.
In practice, as long as the calculations are done in the right order, it shouldn't be tricky.
Might this also explain Mr Picker's claim that filter factors are "wrong."? His solution was to sell a modified meter.
 

Ian Grant

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So, a colour temperature meter to add to the mule's panniers. The LF life is cruel.
In practice, as long as the calculations are done in the right order, it shouldn't be tricky.
Might this also explain Mr Picker's claim that filter factors are "wrong."? His solution was to sell a modified meter.
Well some film data sheets do give filter factors for daylight and tungsten, Ilford do make a comment that more exposure may be needed with Green & Blue filters in the late afternoon and winter months sue to a higher red light level to the daylight.

Filter factors may differ depending on the film used, Kodak give filter factors for common Wratten filter for all their films in Daylight and Tungsten light. On the latest Tmax 100 data sheet they state these may differ with other Kodak films.

Ian
 

Alan9940

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I have tested all my regularly used films to achieve ~0.10 over fb+f; determined via densitometer reading. Most of the films I've tested recently come in at about 1/3 less than box speed, except Tri-X 320 and EFKE 25 which tested out at exactly box speed.

That said, IMO doing sensitometric testing isn't necessary. Assuming normal daylight exposures, start with 1/2 box speed, determine your proper development time, then make images. If you have a solid proofing workflow (yeah, I won't bring up the PP, again!), just watch your shadow areas vs placement on the zone scale. For example, if you placed a deep shadow area in Zone III because you wanted to retain some texture and it reveals as darker than you expected, drop your film speed 1/3 stop. Conversely, if that shadow area is brighter than you expected, then raise your film speed 1/3 stop.

Once you've hit the "sweet spot", forget about it and make beautiful images. Keep an eye on your proofs, and you will know right away if anything about your process, materials, etc, have changed or, maybe, you made a mistake. Hmm, like that ever happens!! :D
 

David M

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All good pragmatic advice, in my view.
Except for "beautiful." However do we do that?
 

Ian-Barber

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I have tested all my regularly used films to achieve ~0.10 over fb+f; determined via densitometer reading. Most of the films I've tested recently come in at about 1/3 less than box speed, except Tri-X 320 and EFKE 25 which tested out at exactly box speed.
Going the other other way, do you do any testing to reach a Zone VIII print value
 

Alan Clark

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Going the other other way, do you do any testing to reach a Zone VIII print value
To my way of thinking the test for negative highlight density is to make wet prints. If you consistently need to use grade 3.5 or 4 to get decent prints, then highlight densities are too low, and your films need more development. If you are constantly printing on grade 1 or 1.5, this is an indication that your films are being over-developed.
On a 120 roll, or 35mm roll, you will, of course, get some frames that need these grades if exposures have been made in a variety of lighting conditions. This is fine, because the targeted "middle of the road" frames will then print on a middle grade, i.e. 2.5 or 3. Individually developed sheets of film should print on these grades of course, if you have got your developing regime sorted out.

Alan
 

Ian-Barber

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If you are constantly printing on grade 1 or 1.5, this is an indication that your films are being over-developed.
Would it be fair to say that if the scene was also low contrast (murky winters day) then increasing the paper grade would not really help
 

Alan Clark

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Would it be fair to say that if the scene was also low contrast (murky winters day) then increasing the paper grade would not really help
Ian, we are now entering the realm of making an expressive print that reflects the subject as you saw it, and how you want it to look in the finished print. Printmaking now becomes a creative activity, in which there are no rules, and no single "best" way to proceed. You are on your own, my friend!
There is a convention or "rule" that a photographic print should have a full range of tones from full black to paper white. A foggy day print may not look convincing if done like this, as I think you are suggesting. But it might. I have seen some that did. And I have seen other foggy scenes that had a limited tonal range -just like the actual subject- and they looked drab and dull as ditchwater…
Blakemore (who often broke the "full range of tones" rule) advised us to produce a "flexible" negative that can be printed in a variety of different ways. Very useful advice. It's in his book, which I think you have.

Alan
 

Ian-Barber

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Blakemore (who often broke the "full range of tones" rule) advised us to produce a "flexible" negative that can be printed in a variety of different ways. Very useful advice. It's in his book, which I think you have.
Yes I have read that statement many times in his book and was intrigued by it
 

David M

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Alan has put his finger on it. The test for everything is the print. Rather like baking a cake, I suppose.
One of John's demonstrations is to produce several prints, all very different, but all desirable, from one negative.
 

Alan9940

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Going the other other way, do you do any testing to reach a Zone VIII print value
Yes, sir, I do. First, I determine the minimum exposure needed to reach dMax of the paper through clear (unexposed) processed film (cover half the paper with something to block the enlarging light.) Then, I replace the clear neg with my Zone VIII negative and give the same exposure as before, using the card to cover half the paper. It's important here to not change anything! Same height of enlarger head, same lens aperture, same paper processing, etc, etc. What you're looking for is a print tonal value that's just slightly darker than paper white. If too gray, then increase film development time; if no difference at all, decrease film development time. You have Fred Picker's Zone VI Workshop book, right? It's all explained in there.

But, again, this is all just the technical side of things. As others have already said, it's the final print that makes all the difference. You're trying to achieve prints that sing...I've made a few of those, and a LOT of also-rans! ;)
 

Alan Clark

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Alan, I have the feeling that you must be using an enlarger with a cold light. What you describe wouldn't work with an enlarger with a tungsten light and multigrade filters - which are designed to be used with a colour temperature of about 2700K, i.e. a tungsten or incandescent bulb. With this system the time required to achieve the merest hint of a highlight varies as you change grades. If you start at grade 0 and work up, the time gets gradually longer and longer into the higher grades. What remains constant is a mid-tone. So if you did your test at grade 2 you would get a longer time if you did it again at grade 3. Thus negating the usefulness of the test.
When I built a 5 x 4 enlarger I used a fluorescent light. And with this the highlight tone stayed the same for a given exposure, right across the grades. So your system would work with it, except I recently changed it to 2700K LED bulbs. The reason? I couldn't get a full contrast range with the fluorescent light, and the contrast change wasn't constant and even between the grades. My new LED bulbs produce results identical to my other enlargers with incandescent bulbs, when used with Multigrade filters.

Alan
 

David M

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This system of testing was devised when only graded papers were available. The intention was to produce a negative that would print on a standard grade, usually, in those days, grade 2. Then the other grades would be used to increase of decrease contrast if that made a more expressive print. Even with variable contrast paper, this is still the aim, although there's no reason why an inquisitive and industrious photographer shouldn't devise a range of Z VIII development times if it seemed useful. I believe that AA originally suggested using ZV as the development target and later changed his mind. I would need to check...

Yes, The Negative, p242 "In previous books I recommended Zone V as the pivotal reference, in relation to earlier films. I am now advising Zone VIII as the reference point for the high negative-density value, because of the long straight-line characteristics of modern emulsions."

The vital point about negative development is that once it's done, its characteristics are frozen, whereas we can make repeated prints at sorts of grades and exposures, until we get it to our satisfaction. It therefore makes sense to have a negative that allows for maximum freedom at the printing stage.
We are back to flexibility.
 

Alan9940

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Alan, I have the feeling that you must be using an enlarger with a cold light.
Well, I do print with a cold light head; started with the old Aristo W45 lamp and at some point--maybe back in the late 80's or early 90's--I moved to the Aristo V54 lamp because I started using VC papers. Full confession... Nowadays, I don't test for Zone VIII as described above now that I have a densitometer. I simply expose a smooth white card in sunlight, using my personal EI, then develop the film until I hit 1.25 - 1.35 over fb+f. Since most folks don't own a densitometer, I thought it best to state a scenario that any photographer with a darkroom can perform.

All that said, I really don't understand why the Zone VIII testing procedure wouldn't work, if you printed with VC papers. If I picked a grade/filter, say #2, to standardize on and developed the film until I saw a hint of tone when using dMax exposure, you're saying that would be totally wrong? Hmm... Funny that I've done Zone VIII testing on 10x8 film, using the method as described above, that I typically contact print on graded chlorobromide papers and, yet, this same sheet of film prints beautifully on Ilford VC Warmtone paper. It could be that the Zone VIII test wouldn't look right on the VC paper...dunno...never tried it.

I guess the takeaway from this thread is that answering technical questions is futile because each of us have our own way of working. And, each of us works at our craft until we find methods and workflows that work for us.
 
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